1. Field of Invention
This invention relates to yellow couplers which provide, upon coupling reaction with the oxidation product of a primary amine developing agent, a dye having an extremely excellent fastness.
2. Description of the Prior Art
In the field of color light-sensitive materials, it has been eagerly desired to keep images in a developed state over a long period of time. To enhance fastness of a dye formed from a coupler is the most fundamental approach to this object. Unlike cyan couplers and magenta couplers, yellow couplers do not provide a dye having improved fastness even when used together with so-called anti-fading agents, but rather provide deteriorated fastness. Therefore, with respect to yellow couplers it has been particularly desired to enhance fastness of the dye formed from the couplers.
Japanese Patent Publication No. 16,058/74 and U.S. Pat. No. 3,892,576 disclose couplers having a structure which might be considered analogous to that of the yellow couplers of the present invention represented by formula (I) below.
The former discloses pyrazolone magenta couplers having a ##STR2## moiety where R.sub.1 and R.sub.2 represent alkyl groups. The invention disclosed therein is directed to reducing the amount of solvent required to incorporate the couplers into a color photographic emulsion and improve the spectral absorption characteristics of color images by utilizing the high solubility of the couplers for high boiling organic solvents and differs from the present invention in construction and object. In addition, yellow couplers show a different behavior from magenta couplers in terms of their photographic properties, and while magenta couplers having a ##STR3## moiety show a high solubility for high boiling organic solvents, it is extremely difficult to predict that yellow couplers having such a moiety would provide extremely fast dyes.
U.S. Pat. No. 3,892,576 discloses introducing a ##STR4## moiety into photographic additives to increase their diffusion resistance.